Various attempts have been made to stabilize the movement of floating structures, such as platforms using submerged units.
U.S. Pat. No. 3,739,737 describes how submerged "damping organs," i.e., horizontal plates, can be fitted beneath the legs of such platforms.
U.S. Pat. No. 3,986,471 describes submerged damping units that are almost as large in extent as the horizontal plan of the respective platform. This damping unit primarily consists of horizontal cellular panels with vertical sluises that, allow water to flow through from below but not from above. In addition there are two longitudinal ballast chambers that are used as pontoons during tow out to operational locations. These chambers can also be completely or partially filled with water to give the damping unit extra weight.
The main purpose of the design is to dampen the heave motion of a platform by acting as a "parachute" whenever the platform moves upwards. As the platform and the damping unit are connected by chains, the unit can only provide damping in a single direction. The complexity of the design and other factors have meant that this invention has never been realized in practice.